Hydraulic pressure modulator

ABSTRACT

An anti-skid braking system which includes a modulator for controlling communication between the master cylinder and the brakes. The modulator allows normal communication until a skid condition is sensed. Upon sensing the skid condition, the modulator releases fluid pressure from the brakes until the skid condition no longer exists and, thereafter, reapplies the fluid pressure to the brakes. This cycle is repeated as many times as the skid condition is sensed.

United States Patent [191 MacDuft [111 3,724,915 51 Apr. 3, 1973 [54]HYDRAULIC PRESSURE MODULATOR [75] Inventor: Stanley Irving MacDutf,Magdalen Islands, Quebec, Canada [73] Assignee: The Bendix Corporation,South Bend, Ind.

[22] Filed: Sept. 16, 1970 [21] 7 Appl. No.: 72,738

' Related U.S. Application Data [62] Division of Ser. No. 763,742, Sept.30, 1968, Pat.

[52] U.S. Cl ..303/2l F [51] Int. Cl. ..B60t 8/06 [58] Field of Search..303/2l F [56] References Cited UNITTBSTATIESPATENTS 3,038,76 1 6/1962'Knrick ..'...'3oa 211= Q 2 66 (Q 58 64 i 3,588,190 6/1971 Nakano et al.....303/2l F Primary ExaminerEvon C. Biunk Assistant Examiner-Merle F.Maffei Attorney-William N. Antonis and Flame, Hartz, Smith and Thompson[5 7] ABSTRACT An anti-skid braking system which includes a modulatorfor controlling communication between the master cylinder and thebrakes. The modulator allows normal communication until a skid conditionis sensed. Upon sensing the skid condition, the modulator releases fluidpressure from the brakes until the skid condition no longer exists and,thereafter, reapplies the fluid pressure to the brakes. This cycle isrepeated as many times as the skid condition is sensed.

12 Claims, 5 Drawing Figures PATENTEUAPR 3 I975 SHEET 1 OF 3 INVENTORSTANLEY MA DUFF I I 144/, wall.

HYDRAULIC PRESSURE MODULATOR SUMMARY This application is a division ofpatent application Ser. No. 763,742, filed on Sept. 30, 1968 now U.S.Pat. No. 3,556,609.

Pressure modulators which have the ability to control communicationbetween hydraulic actuators and motors and automatically terminate thesame to thereby take over the operation of the motors are generally wellknown in the art, as exemplified in U.S. Pat. Nos. 3,093,422 and3,325,226. However, such modulators have not taken into account thecontrol of tandem hydraulic actuation devices for tandem motors that areseparated for fail-safe objectives. For example, the present day vehiclebraking systems are required by Federal Law to provide for separatebrake control systems on the front and rear axles of the vehicle. Inthese applications modulators such as have been suggested in the priorart would be counter to the Federal Law in that they are only able tomodulate a single hydraulic pressure from a single actuator to a singlemotor. Therefore, the principal object of this invention is to provide amodulator which can meet the braking systems required today by theFederal standards.

It is another object of this invention to improve upon the prior arttype of modulators by adding fail-safe provisions to the servomotorsection of the modulator.

A still further object of this invention is to provide a hydraulicpressure modulator with balanced inlet valves that eliminate the effectof pressure created by the hydraulic actuator upon their functioning inthe modulator.

DRAWING DESCRIPTION Other objects and advantages will most certainlyappear to those skilled in the art to which this invention relates froma detailed reading of the description of the drawings in which:

FIG. 1 shows a schematic braking system for a vehicle which provides autilization for a modulator in accordance with the principles of thisinvention;

FIG. 2 is a partial cross sectional view of a modulator as schematicallyillustrated in FIG. 1 for installation in a hydraulic pressure system;

FIG. 3 is a cross sectional view of still another form that themodulator may take and be within the principles set forth by thisinvention; and

FIGS. 4 and 5 are cross sectional views of balanced valves controllingbrake system hydraulic pressure communication via the modulator of FIG.3.

DETAILED DESCRIPTION At the outset it should be appreciated that whilethe invention has been more particularly directed to a modulator for usein a vehicle braking system, that there are several other adaptationsfor such a modulator as proposed by this invention. In particular, it isvisualized that in an industrial application utilizing hydraulicpressure for controlling tooling, or the like, there is need for amodulator such as this invention discloses for controlling the operationof such tooling regardless of the operators commanding hydraulicactuator after a certain hydraulic pressure has been developed in apress, for example.

In any event the present invention finds particular adaptation, asmentioned previously, in a vehicle braksafe for operation on thehighways throughout'the world. As the number of vehicles in operationincreases with each succeeding year, it has been observed that thereasonable conditions heretofore thought available for design purposesare not the most practical today, or for that matter, tomorrow.Therefore, it is the intent of the braking industry to provide a brakesystem which will readily adapt itself to the conditions of operationfor the vehicle to optimize the braking on the vehicle wheels in allconditions of operation. Thus, the present day intent of the vehicleindustry and the brake suppliers is to provide an anti-skid device forthe vehicle at a reasonable cost. Such a system is illustrated in FIG.1, as could be made available to todays vehicles as well as tomorrow's.It involves the use of the fluid pressure servomotor l0 controlling atandem or split master cylinder 12 which is operated by a brake pedal 14within the operators compartment of a vehicle. The master cylinder 12 isconnected by means of conduits l6 and 18 to inlets 20 and 22 of amodulator 24 which also is provided with outlets 26 and 28 to whichconduits 30 and 32 are connected leading to front disc brake actuators34 and 36 and an inlet port 38 of the rear brake load proportioningvalve 40 that has an outlet port 42. With regard to the loadproportioning valve 40, its outlet port 42 has connected to it a conduit44 leading to wheel cylinders 46 and 48 of the vehicles rear brakesystem, shown as drum brakes in this instance. The vehicles front brakeshave breaking discs 50 and 52 to which deceleration sensors 54 and 56are operatively connected to provide a signal corresponding to the wheeldeceleration. This signal is communicated by means of electrical leads58 and 60 to a computer control center 62 which is connected by anelectrical lead 64 to the vehicle's battery 66 and to a source of groundvia electrical lead 68 and switch 70 that is activated upon thedepression of the brake pedal 14. The logic provided by the computer 62is communicated via electrical leads 72 and 74 to solenoid valves 76 and78 of the servomotor 24. The system is completed upon the attaching ofvacuum conduit 80 from the vehicles engine intake manifold 82 andconduit 84 also therefrom to the modulator 24 and servomotor 10,respectively. It should be noted that the brake proportioning valveincludes a lever 86 connected by a spring 88to a bracket 90 attached tothe vehicle frame 92 so as to regulate delivery of hydraulic pressurethrough valve 40 in accordance with the distance separating the frame 92from a rear axle 94 of the vehicle mounting the rear brakes containingwheel cylinders 46 and 48'and also the load proportioning valve 40.

With particular regard now to FIG. 2, the modulator 24 is more clearlydepicted to involve a housing having a front shell 96 and a rear shell98 joined, as by a twist lock assembly 100 with a peripheral bead 102 ofa diaphragm 104 interposed for sealing the juncture of the shells.Within the shell a partition having a central portion 106 with axiallyprojecting front and rear portions 108 and 110 joined thereto isprovided to make sure of the compression of the bead 102 and allow forthe tolerance of construction of the shells 96 and 98.

The central portion 106 of the partition has a dividing 7 wall 112, andthe juncture of portion 106 with portion 108 is sealed by means ofperipheral bead 114 of the diaphragm 116.

Within the chamber formed by the juncture of shells 96 and 98 movablewalls 117 and 118 are sealingly related to diaphragms 104 and 116,respectively, and operatively connected to each other in the structureof FIG. 2 by an abutment as at 120. The walls 117 and 118 may bereinforced, as by means of a metal plate 122 on the wall 118 and bymeans of a button 124 within boss 126 of wall 118 that also contacts theplate 122, as shown. A pair of springs 128 and 130 are installed withinthe front shell 96 so that upon the assembly of the shells 96 and 98they are both compressed between the wall 118 and the end of the shell96. If desired, one spring could be used for this positioning of thewalls 118 and 117 in their rest attitude as shown by FIG. 2. However,for the purposes of fail-safe construction the invention concerns itselfwith the utilization of two springs in order that if one should happento break during the life of themodulator the other will be sufficient toperform the modulator functions. Shell 98 is provided with openings 132,134 and 136 on its rearwardmost face to which the solenoid valve 76, ahydraulic cylinder 138 and the solenoid valve 78 are connected such asby flanges thereon and bolts as illustrated by bolt 140 on flange 142for the cylinder 138.

Within each of the solenoid valves 76 and 78 there is provided a coil144 and a core 146 for controlling poppets 148 and 150 that aresuspended in the valves 76 and 78 by slotted spring fingers 152 and 154;and the housing structure of the valve 76 and 78 is arranged incooperation with the slotted spring fingers 152 and 154 to maintainpoppet 148 normally closing the passageway through valve 76 to a controlchamber 156 of modulator 24 and to keep poppet 150 normally open wherebycommunication from a conduit 158 is open around the slotted fingers 154to the chamber 156. As seen, conduit 158 is connected to check valvestructure 160 which is communicated to conduit 80 leading from thevehicle engine intake manifold 82 (see FIG. 1) so that vacuum is alwayspresent within the conduit 158 and into an annular chamber 162 about thepartition constructed from members 106, 108 and 110. In this regard itshould be noted that member 110 is provided with a plurality of radialopenings 164 and that notches 166 and 168 are provided at the junctureof elements 106 and 108 and at the end of element 108, respectively, tocommunicate chamber 162 to chambers 170 and 172 on similar sides ofwalls 117 and 1 18, respectively. Likewise, chamber 156 is communicated,via passage 174 internally of the wall 117 to the notches 176 on theforward face of wall 1 18, to a chamber 178 on a similar side of wall118, whereby chambers 156 and 178 are on opposite sides of the wallsthen the chambers and 172.

Cylinder 138 is bored for the receipt of plungers 180 and 182 whichplungers create chambers 184 and 186 in the bore of the cylinder 138. Toeach of these chambers 184 and 186 separate inlets 188 and 190 as wellas separate outlets 192 and 194 are communicated in the housing forcylinder 138. In the inlets 188 and 190 spring biased ball valves 196and 198 are operatively related to pins 200 and 202, the former of whichis connected by link 204 to plate 206 on plunger 180 and the latter ofwhich is connected to or abutting on plunger 182. The pin 200 and itslink 204 have fluted bodies in order to permit fluid communicationbetween the chamber 184 and outlet 192 as well as from inlet 188 tochamber 184 and/or outlet 192.

Solenoid valve 78 has orifices 207 provided in the peripheral regions ofits wall 209 having valve seat 211 as does wall 213 for valve 76.

With regard now to FIG. 3 there is shown a modified modulator 208 thatcan be substituted for the modulator 24 in FIG. 1. This modulatorinvolves the use of an intermediate shell 210 with rear shell 212 and afront shell 214 that are joined, all together, by a band clamp 216 and218 with peripheral walls 220 and 222 of rolling diaphragms 224 and 226interposed to seal the joint. Diaphragms 224 and 226 are affixed bymeans of threadless fasteners 228 and 230 to hub structures 232 and 234that are threadedly joined together as at 236 to provide variable volumechambers 238, 240, 242 and 244 within the servomotor section ofmodulator 208. As with the modulator 24, the communication of controlchambers 240 and 244 is via internal passage246 of the hubs 232 and 234.In contrast to the modulator 24 the communication of chambers 238 and242 is via an external conduit 248 connected to vacuum check valve 250to which also conduit 252 is communicated leading to solenoid valve 254which, in addition to solenoid valve 256 controls the response of themovable walls in the modulator 208. Diaphragm 222 and 224 have diaphragmsupport plates 258 and 260 also held by threadless fasteners 228 and 230to the hubs 232 and 234. The solenoids for valves 254 and 256(comprising coils 144 and cores 146 as in FIG. 2) are connected by meansof electric terminals 262 and 264 to electrical leads 74 and 72,respectively.

The modulator 208 of FIG. 3 has a modified hydraulic cylinder housing266 wherein a hydraulic plunger 268 is provided with a chamfer 270 and aprojection 272 abutting a floating piston 274 forming the other portionof the plunger means for the cylinder 266. The chamfer 270 cooperateswith a cam face 276 of a balanced valve 278 controlling communication ofinlet 280 with a chamber 282 open by means of an outlet port 284. Asimilar balanced valve 286 cooperates with the notched head 288 offloating piston 274 for controlling an inlet port 289 communicating withchamber 291 and outlet'port 290. The balanced valves 278 and 286 areassembled by means of plugs 292 and 294 into appropriate openings in thecylinder housing 266. When it is said that valves 278 and 286 arebalanced valves, it is meant that the valve stem portion 296 and 298 isequal in diameter to the seating area of valve heads 300 and 302 andeach of the valves are provided with longitudinal through passages 301and 303 so that hydraulic pressure on all surfaces of the valve isbalanced and only forces of valve springs 304 and 306 enter into thecontrol of the valves.

It should be noted that lip seals 308 and 310 seal the stems 296 and 298about their receiving bore of plugs 292 and 294 such that pressure inchambers 282 and 291 can, in the event of being higher than pressures atports 280 and 289, bleed by the seals to relieve the pressures inchambers 282 and 291. In this way positive release of hydraulic pressurein the brake system disclosed can be assured by the seals which preventleak down so long as brake pressure is demanded.

OPERATION In operation the vehicle operator upon depressing brake pedal14 will close contacts in switch 70 to energize the computer controlcenter 62. In addition he will provide hydraulic pressure via conduits16 and 18 to the inlets 20 and 22 (ports 188 and 190 of the modulator 24shown in .FIG. 2) which will initially be exhausted via chambers 184 and186 to the outlets 26 and 28 (ports 192 and 194), respectively, toconduits 30 and 32 leading to the front disc brake actuators 34 and 36and the load proportioning valve 40 respectively. Initially, also, thisbrake pressure in conduit 32 will be communicated through the loadproportioning valve 40 ,via conduit 44 to wheel cylinders 46 and 48 foractuation of the rear brakes of the vehicle. In the event of a loadshift, which can be expected to occur soon thereafter, the communicationof conduit 44 to wheel cylinders 46 and 48 will be gradually modulatedby valve 40 because of the effect of the load shaft on the distancebetween the frame 92 and the axle 94.

Either prior to this deceleration causing a load shift of after it,sensors 54 and 56 may sense a corresponding deceleration of brake discs50 and 52'which tell the computer center 62 to create logic signals inleads 72 and 74 to first of all close poppet 150 by the electromagneticattraction of core 146 upon energization of coil 144 of the poppet 150towards the seat of the housing for valve 78. This will, upon seating ofpoppet 150, terminate the communication of vacuum in conduit 158 tochambers 156 and, via passage 174, notches 176, chamber 178. If thecomputer control center 62 further requires that the rapid rate ofdeceleration be retarded, valve 76 will be energized so that theelectromagnetic action of core 146, caused by energization of coil 144,will pull poppet 148 off its seat to communicate atmospheric air intochamber 156 and via passage 174 notches 176 to chamber 178. Thus apressure differential will be created across walls 117 and 118 to movethese walls in opposition to the force of springs 128 and 130. This willwithdraw plunger 180 whose withdrawal will be followed up by means offloating piston 182 but to a lesser extent in view of the fact thatpiston 182 has not only the pressure of chamber 186 acting on it butalso the pressure chamber 184. This first permits closure of valves 196and 198 terminating communication of master cylinder 12 with chambers184 and 186. Further movement of plunger 180 increases the displacementfor the front and rear braking system beyond the modulator 24 and willthereby lessen the rate of retardation until the sensors 54 and 56 tellthe computer control center 62 to curtail the operation of modulator 24.

After the desired displacement increase in reference to signals fromcomputer control 62, the solenoid valves 76 and 78 will both be closed;i.e., blocking opening 132 and on seat 21 1, respectively. However, asspring fingers 154 have openings allowing communication of vacuum inconduit 158 via openings 207 to chambers 156 and 178, there will be agradual expansion of springs 128 and 130 to slowly build brake pressurefrom ports 193 and 194 until sensors 54 and/or 56 again sense wheel lockand control 62 responds, as before. These passages 207 are to be small,and, thus the opening of poppet 148 to communicate atmospheric pressureto opening 132 will not be affected by them.

Upon release of the vehicle brakes 14, switch is opened to deactivatethe computer control center 62 and the walls 117 and 118 are againsuspended in vacuum whereby springs 128 and will return plunger means180, 1.82 to the rest position and brake fluid from the brake system isreturned to the reservoirs for the split master cylinder 12; i.e.,plunger and floating piston 182 open valves 196 and 198. The system isnow ready for reapplication. Lip seals 308 and 310 shown in thestructure of FIG. 3 aid in eliminating delay in the establishment ofreturn flow to provide a faster response and return to normal.

Having fully described an operative construction of at least twoembodiments visualized so far for my invention, it is now desired to setforth the intended claims for these Letters Patent as follows.

I claim:

1. A brake pressure modulator comprising:

a housing inclusive of a fluid pressure chamber and a hydrauliccylinder;

a pressure responsive wall means in said chamber;v

spring means to bias said wall means to a normal position in saidhousing; first and second plungers in said cylinder operativelyconnected to said wall means and to each other, said first and secondplungers defining first and second variable volume chambers in saidcylinder and one of same being exposed to pressures of both variablevolume chambers, said chambers each having its own inlet and outletports; and

valve means for said modulator including first valve elements forcontrolling said pressure responsive means and second valve elementswith portions in each fluid inlet with one portion operatively connectedto said first plunger and another portion operatively connected to saidsecond plunger to control communication between inlet and outlet portsand isolation of same.

2. The structure of claim 1 wherein said spring means includes twosprings to render said modulator fail-safe which two springs are locatedto maintain the normal position of said plungers in the event of afailure in said pressure responsive means to keep open the communicationbetween inlet and outlet ports.

3. The structure of claim 1 wherein said valve elements arehydraulically balanced poppets urged to a closed position by springmeans that is normally compressed by action of said plungers to maintainsaid poppets off their seats provided by surrounding structure.

4. The structure of claim 3 wherein said poppets have a stem of adiameter equal to the seat are'a therefor and a passage therethrough toequate pressures on all surfaces of said poppet.

5. The structure of claim 4 wherein a lip seal means is provided on saidvalve stem permitting return flow from said passage therethrough andblocking flow in the opposite direction.

6. A brake pressure modulator for use in a braking system, saidmodulator comprising:

a housing including a pressure chamber;

movable wall means contained within said pressure chamber, said movablewall means being responsive to a pressure'difference thereacross;

first and second valve means in said housing for controlling the flow ofseparate pressurized fluids; first and second plunger means operativelyconnected to said movable wall means to control said first and secondvalve means, respectively;

means for biasing said movable wall means to a normal position, saidnormal position allowing flow of said separate fluid pressures throughsaid first and second valve means; and

means for controlling said pressure difference across said movable wallmeans in response to control signals, movement of said movable wallmeans away from said normal position terminating flow through said firstand second valve means by movement of said first and secondplunger,respectively, and reducing the pressure of the fluid alreadydelivered through said first and second valve means by further movementof said first and second plungers.

7. The brake pressure modulator, as recited in claim 6, wherein saidfirst plunger has said separate pressurized fluids communicated toopposite ends thereof to equalize pressures delivered through said firstand second valve means.

8. The brake pressure modulator, as recited in claim 6, wherein saidcontrolling means is operated by a first and a second of said controlsignals, while receiving said first control signal, a first controlvalve terminates one source of fluid power to said pressure chamber and,upon receiving said second control signal, a second valve establishesanother source of fluid power to said pressure chamber to move saidmovable wall means from its normal position.

9. In an adaptive braking modulator:

a housing defining a bore and a chamber therewithin;

said bore being divided into first and second compartments, each of saidcompartments having an inlet and an outlet port;

valve means mounted in each of said compartments for controllingcommunication between each of said inlet ports and their correspondingoutlet ports;

pressure differential responsive means mounted in said chamber;

plunger means operably connecting said pressure differential responsivemeans and each of said valve means for operating the latter wherebymovement of said pressure differential responsive means in one directioncloses said valve means and movement of said pressure differentialresponsive means in the opposite direction opens said valve means.

10. The invention of claim 9:

said plunger means including an element operating one of said valvemeans; said element having a pair of opposed faces, one of said facesbeing exposed to the fluid pressure level in one of said compartments,the other face of said element being exposed to the fluid pressure levelin the other compartment.

1 1. The invention of claim 10:

said bore including a cavity, opposite faces of said element beingexposed to the fluid pressure level in said cavity and in one of saidcompartments;

said plunger means including a member extending from said cavity intothe other chamber.

12. The invention of claim 9:

said bore including a cavity;

said plunger means including a rod-like member operatively engaging saidpressure differential responsive means and extending into said cavity,an element having a pair of opposed faces exposed to the fluid pressurelevel in said cavity and in one of said compartments, said rod-likemember engaging the face of said element exposed to the fluid pressurelevel in said cavity, and a member operatively connected to saidrod-like member and extending from said cavity into the other chamber.

slidably

1. A brake pressure modulator comprising: a housing inclusive of a fluid pressure chamber and a hydraulic cylinder; a pressure responsive wall means in said chamber; spring means to bias said wall means to a normal position in said housing; first and second plungers in said cylinder operatively connected to said wall means and to each other, said first and second plungers defining first and second variable volume chambers in said cylinder and one of same being exposed to pressures of both variable volume chambers, said chambers each having its own inlet and outlet ports; and valve means for said modulator including first valve elements for controlling said pressure responsive means and second valve elements with portions in each fluid inlet with one portion operatively connected to said first plunger and another portion operatively connectEd to said second plunger to control communication between inlet and outlet ports and isolation of same.
 2. The structure of claim 1 wherein said spring means includes two springs to render said modulator fail-safe which two springs are located to maintain the normal position of said plungers in the event of a failure in said pressure responsive means to keep open the communication between inlet and outlet ports.
 3. The structure of claim 1 wherein said valve elements are hydraulically balanced poppets urged to a closed position by spring means that is normally compressed by action of said plungers to maintain said poppets off their seats provided by surrounding structure.
 4. The structure of claim 3 wherein said poppets have a stem of a diameter equal to the seat area therefor and a passage therethrough to equate pressures on all surfaces of said poppet.
 5. The structure of claim 4 wherein a lip seal means is provided on said valve stem permitting return flow from said passage therethrough and blocking flow in the opposite direction.
 6. A brake pressure modulator for use in a braking system, said modulator comprising: a housing including a pressure chamber; movable wall means contained within said pressure chamber, said movable wall means being responsive to a pressure difference thereacross; first and second valve means in said housing for controlling the flow of separate pressurized fluids; first and second plunger means operatively connected to said movable wall means to control said first and second valve means, respectively; means for biasing said movable wall means to a normal position, said normal position allowing flow of said separate fluid pressures through said first and second valve means; and means for controlling said pressure difference across said movable wall means in response to control signals, movement of said movable wall means away from said normal position terminating flow through said first and second valve means by movement of said first and second plunger, respectively, and reducing the pressure of the fluid already delivered through said first and second valve means by further movement of said first and second plungers.
 7. The brake pressure modulator, as recited in claim 6, wherein said first plunger has said separate pressurized fluids communicated to opposite ends thereof to equalize pressures delivered through said first and second valve means.
 8. The brake pressure modulator, as recited in claim 6, wherein said controlling means is operated by a first and a second of said control signals, while receiving said first control signal, a first control valve terminates one source of fluid power to said pressure chamber and, upon receiving said second control signal, a second valve establishes another source of fluid power to said pressure chamber to move said movable wall means from its normal position.
 9. In an adaptive braking modulator: a housing defining a bore and a chamber therewithin; said bore being divided into first and second compartments, each of said compartments having an inlet and an outlet port; valve means mounted in each of said compartments for controlling communication between each of said inlet ports and their corresponding outlet ports; pressure differential responsive means slidably mounted in said chamber; plunger means operably connecting said pressure differential responsive means and each of said valve means for operating the latter whereby movement of said pressure differential responsive means in one direction closes said valve means and movement of said pressure differential responsive means in the opposite direction opens said valve means.
 10. The invention of claim 9: said plunger means including an element operating one of said valve means; said element having a pair of opposed faces, one of said faces being exposed to the fluid pressure level in one of said compartments, the other face of said element being exposed to the flUid pressure level in the other compartment.
 11. The invention of claim 10: said bore including a cavity, opposite faces of said element being exposed to the fluid pressure level in said cavity and in one of said compartments; said plunger means including a member extending from said cavity into the other chamber.
 12. The invention of claim 9: said bore including a cavity; said plunger means including a rod-like member operatively engaging said pressure differential responsive means and extending into said cavity, an element having a pair of opposed faces exposed to the fluid pressure level in said cavity and in one of said compartments, said rod-like member engaging the face of said element exposed to the fluid pressure level in said cavity, and a member operatively connected to said rod-like member and extending from said cavity into the other chamber. 